The quality and reliability of Narcissistic Supply are, therefore, of paramount importance. The more the narcissist convinces himself that his sources are perfect, grand, comprehensive, authoritative, omniscient, omnipotent, beautiful, powerful, rich, brilliant, and so on â the better he feels. The narcissist has to idealise his Supply Sources in order to highly value the supply that he derives from them. This leads to over-valuation. The narcissist forms a fantastic picture of his sources of Narcissistic Supply.
The fall is inevitable. Disillusionment and disappointment set in. The slightest criticism, disagreement, or differences of opinion are interpreted by the narcissist as an all out assault against the foundations of his existence. The previous appraisal is sharply reversed: the same people are judged stupid who were previously deemed to possess genius, for instance.
This is the devaluation part of the cycle and it is very painful to both the narcissist and the devalued (for very different reasons, of course). The narcissist mourns the loss of a promising "investment opportunity" (Source of Narcissistic Supply). The "investment opportunity" mourns the loss of the narcissist.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 3 DVDs with 16 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)